The invention generally relates to imaging systems, and relates in particular to imaging systems that employ an illumination modulator.
Imaging system such as those disclosed in U.S. Pat. No. 6,433,934, may include an illumination source, a field lens system, an illumination modulator, imaging optics and an imaging surface. During imaging, the field lens system directs the illumination field onto the light modulator and the light modulator reflects the illumination field toward the imaging surface in one mode and reflects the illumination field away from the imaging surface in another mode. For example, the modulator may include a Grating Light Valve (GLV) as sold by Silicon Light Machines of Sunnyvale, Calif., and the system may direct via the imaging optics either the zero order reflection or the first order reflection toward the imaging surface in various embodiments.
Many imaging systems employ an illumination field that is generally in the shape of a line of illumination, permitting a line of picture elements (or pixels) to be imaged simultaneously. It has been discovered, however, that certain modulators may become mis-aligned during manufacturing or use, detracting from the performance of the system and quality of the recorded images. Such mis-alignment may result in the line of illumination being shifted, rotated or bent (e.g., into a curve) with respect to the desired illumination line position in the imaging system.
There is a need, therefore, for a system and method for efficiently and economically determining whether a modulated illumination field from a light modulator is mis-aligned.